Study On Habitat Characterization And Regionalization Of Sassafras Tzumu(Hemsl.) Hemsl.Community In Zhejiang

The habitat of vegetation is the material basis of the community and the entire ecosystem.The niche breadth,the niche overlap,and the interspecific association also play an important role in the field of community ecology research.Therefore,the study of niche and interspecies relations based on the vegetation habitat is of great significance for understanding ecosystem functions.The 189 plot communities in the non-commercial forest county-level monitoring database in Zhejiang Province are selected,of which the niche breadth,niche overlap and interspecific association characteristics are analyzed.The TWINSPAN classification and canonical correspondence analysis methods in quantitative ecology research are used for sorting.Based on this,the biodiversity of the association is carried out.Explore the interaction relationship between plant spatial distribution patterns and environmental factors.The MaxEnt is used to simulate whether S.tzumu is suitable for climatic conditions and planting area.It provides a reference for the management of non-commercial forests,and provides a theoretical basis for the conversion of pine forest to broad-leaved forest,the establishment of precious tree community and the selection of habitat.The main findings are as follows:1.Among the 189 monitoring plots in the study area,there are 149 species of arbor trees,the main dominant species(sorted by important values)are Cunninghamia lanceolata,Pinus massoniana Lamb.,Schima superba,Liquidambar formosana Hance,Cyclobalanopsis glauca(Thunb)Oerst,Castanopsis sclerophylla,Lithocarpus glaber(Thunb.)Nakai,S.tzumu.Through the simulation of environmental factors trends by importance values,the typical habitat of S.tzumu in Zhejiang Province is:height 400-800 m,slope 20°-40°,Shady slope half shady slope,an area with thick and fertile soil.2.The order of niche breadth in the community where S.tzumu located is C.lanceolata,S.tzumu,P.massoniana,S.superba,L.formosana,C.glauca,C.sclerophylla,C.mollissima,they can be seen that C.lanceolata,S.tzumu,P.massoniana,S.superba,have strong adaptability to environment,it appear in many times in plots,and its ability of resource utilization is obvious.S.tzumu has a niche breadth of 61.65,which is second only to C.lanceolata's 89.64,and even greater than P.massoniana 57.28.The niche overlap between S.tzumu and Cerasus serrula(Franch.)Yüet Li is as high as 0.9.The niche overlap values of S.tzumu and C.serrulaare 0.831,S.tzumu and Broussonetia papyriferais 0.785,S.tzumu and Acer palmatum Thunb.is 0.531.3.TWINSPAN is used to classify the plots,the sample plots are divided into eight associations.The name of the association mainly take the indicator based on TWINSPAN as the name of the result of the association division.The biodiversity of 8 associations is analyzed by TWINSPAN,and the index of biodiversity of tree layers of each association is shown in graph.It can be seen from the graph that the variation trend of Simpson index(D),Shannon-Winner index(H)and Pielou evenness index(J)are basically the same.4.CCA shows that the highest correlation coefficient between the eight environmental factors and the first axis is altitude,which is positively correlated.The correlation coefficient is 0.667.The correlation coefficient between the second axis and slope position is 0.547,it is the highest.It can be concluded that altitude and aspect are the determinants of S.tzumu community distribution.5.Based on MaxEnt and ArcGIS to predict S.tzumu potential distribution in Zhejiang,the average AUC value of 15 simulations is 0.829,and the standard deviation is 0.037.It shows that the model has high simulation level and high reliability and reference value.The simulation results show that S.tzumu is located in the high-yield area of Zhejiang Province(distribution value 0.62-1),mainly located in the Dapan Mountains and Tianlao Mountain in the middle of Zhejiang Province,and the Jingshan Mountains,Mogan Mountains and Tianmu Mountains in the north of Zhejiang Province.Among them,the most suitable areas are mainly located in the area of Dapan Mountain and Mogan Mountain.The moderately suitable areas cover most areas of Zhejiang Province,except for the Qiandao Lake Basin,the coastal areas of eastern Zhejiang and northern Zhejiang,and other low suitable areas.The rest of the high suitable areas are mid suitable areas,and it can be seen that S.tzumu has great potential in Zhejiang Province.Altitude,precipitation in the driest season and mean temperature in the coldest season are the main factors affecting the distribution of S.tzumu.The altitude is 550-900m(the result is close to the importance valuefitting),precipitation of the warmest quarterthe is 550 mm,Precipitation of the driest quarter is 300-550 mm,and the mean temperature in the coldest season is 0-2 ?.